Method of forming topology-controlled amorphous carbon polymer film

ABSTRACT

In exemplary embodiment, a method of top-selective deposition using a flowable carbon-based film on a substrate having a recess defined by a top surface, sidewall, and a bottom, includes steps of: (i) depositing a flowable carbon-based film in the recess of the substrate in a reaction space until a thickness of the flowable carbon-based film in the recess reaches a predetermined thickness, and then stopping the deposition step; and (ii) exposing the carbon-based film to a nitrogen plasma in an atmosphere substantially devoid of hydrogen and oxygen so as to redeposit a carbon-based film selectively on the top surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/876,589, filed on Jul. 19, 2019, in the United States Patent andTrademark Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention generally relates to a method of forming atopology-controlled carbon-based film on a patterned recess of asubstrate, particularly to a method of top-selective deposition using aflowable carbon-based film on the patterned recess.

Description of the Related Art

In processes of fabricating integrated circuits such as those forshallow trench isolation, inter-metal dielectric layers, passivationlayers, etc., it is often necessary to fill trenches (any recesstypically having an aspect ratio of one or higher) with insulatingmaterial. However, with miniaturization of wiring pitch of large scaleintegration (LSI) devices, void-free filling of high aspect ratio spaces(e.g., AR≥3) becomes increasingly difficult due to limitations ofexisting deposition processes.

In view of the above, the present inventor developed a gap-filltechnology for deposition of flowable film and disclosed the technologyin U.S. patent application Ser. No. 16/026,711, filed Jul. 3, 2018, andSer. No. 16/427,288, filed May 30, 2019, which provide completegap-filling by plasma-assisted deposition using a hydrocarbon precursorsubstantially without formation of voids under conditions where anitrogen, oxygen, or hydrogen plasma is not required, each disclosure ofwhich is herein incorporated by reference in its entirety.

However, if a certain application, where a sacrificial etch stop layeror protection layer, for example, is necessary only on the top surfaceof a recess, requires top-only deposition of amorphous carbon using theabove gap-fill technology on a substrate without deposition in trenches,e.g., at the bottom of trenches, of the substrate, there might be thefollowing issues: i) deposition by the gap-fill technology isessentially bottom-up deposition, and thus, a certain amount of film mayinevitably be deposited at the bottom of the recess; ii) in the eventthat a recess is an ultradeep hole (having an aspect ratio of, e.g.,more than 10, typically 15-100) used in applications such as 3D NAND,the gap-fill technology can be bottomless deposition (since flowablematerial although it flows downward cannot reach the bottom of therecess), but due to the flowing material along the sidewalls of therecess, a certain amount of film may inevitably be deposited on thesidewalls of the recess; iii) in (ii), a film is deposited on the topsurface. But since the upper opening of the recess is small, the openingmay be closed up, eventually depositing and accumulating a film evenlyon the top surface, and iv) in the event that the upper opening of therecess is wide enough to let the flowable material flow into the recess,it may be difficult to deposit a thick film on the top surface, i.e., itmay be difficult to control the thickness of the film depositing on thetop surface. The present inventor provides herein a landmark solution tothe above issues using the gap-fill technology.

Any discussion of problems and solutions involved in the related art hasbeen included in this disclosure solely for the purposes of providing acontext for the present invention, and should not be taken as anadmission that any or all of the discussion were known at the time theinvention was made.

SUMMARY OF THE INVENTION

In view of the above, some embodiments provide a method of top-selectivedeposition using a flowable carbon-based film on a substrate having arecess defined by a top surface, sidewall, and a bottom, comprisingsteps of: (i) depositing a flowable carbon-based film in the recess ofthe substrate in a reaction space until a thickness of the flowablecarbon-based film in the recess reaches a predetermined thickness, andthen stopping the deposition step; and (ii) exposing the carbon-basedfilm to a nitrogen plasma in an atmosphere substantially devoid ofhydrogen and oxygen so as to redeposit a carbon-based film selectivelyon the top surface. In the above, it is totally surprising that, as aphenomenon, the flowable material once accumulated in the recess, suchas fluid accumulated in a reservoir, can be moved upward and accumulateon the top surface as if fluid is pumped up with a siphon. In anembodiment, by a combination of flowability of the film and nitrogenplasma, the carbon-based film can be redeposited from the bottom of therecess to selectively the top surface. In some embodiment, since theflowable film needs to accumulate at the bottom of the recess bybottom-up deposition, the recess needs to have an aspect ratio of 2 to30 (typically 3 to 20). The gap-fill technology for deposition offlowable film is disclosed in, for example, U.S. patent application Ser.No. 16/026,711, filed Jul. 3, 2018, and Ser. No. 16/427,288, filed May30, 2019, each disclosure of which is incorporated by reference in itsentirety, and such technology can be applied to some embodiments of thepresent invention.

In some embodiments, in order to redeposit a carbon-based film on thetop surface, the carbon-based flowable film accumulating at the bottomof the recess is exposed to a nitrogen plasma, wherein the plasma issubstantially devoid of H₂ and O₂, e.g., a concentration of H₂ and O₂ intotal in the atmosphere of the reaction space is less than 5%,preferably less than 1%. When the concentration of H₂ and O₂ in theatmosphere exceeds the above, the plasma more manifests aching function,rather than contributing to redeposition of the film. Further, in someembodiments, a rare gas such as Ar and He may be contained in theatmosphere of the reaction space when exposing the carbon-based flowablefilm at the bottom of the recess to the plasma, to the extent that theaddition of rare gas does not materially affect the redeposition of acarbon-based film, e.g., a concentration of rare gas (e.g., Ar and/orHe) in total is less than 50%, preferably less than 30%, more preferablyless than 20%, most preferably less than 15%. In some embodiments, theatmosphere consists essentially of or consists of nitrogen gas. In someembodiments, in order to realize flowability of a carbon-based film orbottom-up deposition when depositing the carbon-based film, thedeposition temperature is adjusted, wherein flowability of the film isinversely proportional to the deposition temperature which is adjusteddepending on the type of the precursor, e.g., at a temperature of lowerthan about 100° C., e.g., about 75° C.

For purposes of summarizing aspects of the invention and the advantagesachieved over the related art, certain objects and advantages of theinvention are described in this disclosure. Of course, it is to beunderstood that not necessarily all such objects or advantages may beachieved in accordance with any particular embodiment of the invention.Thus, for example, those skilled in the art will recognize that theinvention may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other objects or advantages as may be taught orsuggested herein.

Further aspects, features and advantages of this invention will becomeapparent from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will now be described withreference to the drawings of preferred embodiments which are intended toillustrate and not to limit the invention. The drawings are greatlysimplified for illustrative purposes and are not necessarily to scale.

FIG. 1A is a schematic representation of a PEALD (plasma-enhanced atomiclayer deposition) apparatus for depositing a dielectric film usable inan embodiment of the present invention.

FIG. 1B illustrates a schematic representation of a precursor supplysystem using a flow-pass system (FPS) usable in an embodiment of thepresent invention.

FIG. 2 is a chart illustrating schematic cross sectional views oftrenches showing processes of top-selected deposition ((a)→(b)→(c))according to embodiments of the present invention.

FIG. 3 is a chart illustrating schematic cross sectional views oftrenches showing a prospective mechanism of top-selected deposition((a)→(b)→(c)→→(d)) according to embodiments of the present invention.

FIG. 4 is a graph showing shrinkage of films exposed to plasma ofdifferent gases.

FIG. 5 shows STEM photographs of cross-sectional views of trenches,wherein raw (a) represents trenches subjected to full-fill deposition offlowable film, raw (b) represents the trenches shown in (a) after O₂/Arashing, and raw (c) represents the trenches shown in (a) after N₂/H₂ashing, and column (1) represents the trenches at a high magnification(the scale bar represents 60 nm), and column (2) represents the trenchesat low magnification (the scale bar represents 300 nm).

FIG. 6 shows: (a) a STEM photograph of a cross-sectional view oftrenches subjected to flowable film deposition at 75° C., followed byexposure to N₂ plasma according to an embodiment of the presentinvention, and (b) a STEM photograph of a cross-sectional view oftrenches subjected to barely-flowable film deposition at 100° C.,followed by exposure to N₂ plasma.

FIG. 7 shows: (a) a STEM photograph of a cross-sectional view oftrenches subjected to flowable film deposition, followed by exposure toN₂ plasma for 10 seconds, and (b) a STEM photograph of a cross-sectionalview of trenches subjected to flowable film deposition, followed byexposure to N₂ plasma for 60 seconds according to an embodiment of thepresent invention.

FIG. 8 shows a STEM photograph of a cross-sectional view of trenchessubjected to top-selected deposition according to an embodiment of thepresent invention.

FIG. 9 shows Fourier Transform Infrared (FTIR) spectrums of flowableamorphous carbon polymer film as deposited (“STD”), and redepositedamorphous carbon polymer film with N₂ plasma treatment (“N2-CK”)according to an embodiment of the present invention.

FIG. 10 is a chart illustrating the sequence of processes oftop-selected film formation according to an embodiment of the presentinvention, wherein the width of each column does not necessarilyrepresent the actual time length, and a raised level of the line in eachrow represents an ON-state whereas a bottom level of the line in eachrow represents an OFF-state.

DETAILED DESCRIPTION OF EMBODIMENTS

In this disclosure, “gas” may include vaporized solid and/or liquid andmay be constituted by a single gas or a mixture of gases, depending onthe context. Likewise, an article “a” or “an” refers to a species or agenus including multiple species, depending on the context. In thisdisclosure, a process gas introduced to a reaction chamber through ashowerhead may be comprised of, consist essentially of, or consist of asilicon-free hydrocarbon precursor and an additive gas. The additive gasmay include a plasma-generating gas for exciting the precursor to forman amorphous carbon polymer when RF power is applied to the additivegas. The additive gas may be an inert gas which may be fed to a reactionchamber as a carrier gas and/or a dilution gas. The additive gas maycontain no reactant gas for oxidizing or nitriding the precursor.Alternatively, the additive gas may contain a reactant gas for oxidizingor nitriding the precursor to the extent not interfering with plasmapolymerization forming an amorphous carbon-based polymer. Further, insome embodiments, the additive gas contains only a plasma-generating gas(e.g., noble gas). The precursor and the additive gas can be introducedas a mixed gas or separately to a reaction space. The precursor can beintroduced with a carrier gas such as a rare gas. A gas other than theprocess gas, i.e., a gas introduced without passing through theshowerhead, may be used for, e.g., sealing the reaction space, whichincludes a seal gas such as a rare gas. In some embodiments, the term“precursor” refers generally to a compound that participates in thechemical reaction that produces another compound, and particularly to acompound that constitutes a film matrix or a main skeleton of a film,whereas the term “reactant” refers to a compound, other than precursors,that activates a precursor, modifies a precursor, or catalyzes areaction of a precursor, wherein the reactant may provide an element(such as O, C, N) to a film matrix and become a part of the film matrix,when in an excited state. The term “plasma-generating gas” refers to acompound, other than precursors and reactants, that generates a plasmawhen being exposed to electromagnetic energy, wherein theplasma-generating gas may not provide an element (such as O, C, N) to afilm matrix which becomes a part of the film matrix. The term“plasma-aching gas” refers to a gas which ashes a film when in a stateexcited either directly (direct plasma) or remotely (remote plasma). Insome embodiments, the “plasma-aching gas” is a single gas or a mixed gasof two or more gases. The term “aching” refers to removal of organicmatter using a plasma, leaving mineral components behind as a residue(ash) which is typically removed with a vacuum pump.

In some embodiments, “film” refers to a layer continuously extending ina direction perpendicular to a thickness direction substantially withoutpinholes to cover an entire target or concerned surface, or simply alayer covering a target or concerned surface. In some embodiments,“layer” refers to a structure having a certain thickness formed on asurface or a synonym of film or a non-film structure. A film or layermay be constituted by a discrete single film or layer having certaincharacteristics or multiple films or layers, and a boundary betweenadjacent films or layers may or may not be clear and may be establishedbased on physical, chemical, and/or any other characteristics, formationprocesses or sequence, and/or functions or purposes of the adjacentfilms or layers. Further, in this disclosure, any two numbers of avariable can constitute a workable range of the variable as the workablerange can be determined based on routine work, and any ranges indicatedmay include or exclude the endpoints. Additionally, any values ofvariables indicated (regardless of whether they are indicated with“about” or not) may refer to precise values or approximate values andinclude equivalents, and may refer to average, median, representative,majority, etc. in some embodiments. Further, in this disclosure, theterms “constituted by” and “having” refer independently to “typically orbroadly comprising”, “comprising”, “consisting essentially of”, or“consisting of” in some embodiments. In this disclosure, any definedmeanings do not necessarily exclude ordinary and customary meanings insome embodiments.

In this disclosure, “continuously” refers to without breaking a vacuum,without interruption as a timeline, without any material interveningstep, without changing treatment conditions, immediately thereafter, asa next step, or without an intervening discrete physical or chemicalstructure between two structures other than the two structures in someembodiments.

In this disclosure, the term “filling capability” (also referred to as“flowability”) refers to a capability of filling a gap substantiallywithout voids (e.g., no void having a size of approximately 5 nm orgreater in diameter) and seams (e.g., no seam having a length ofapproximately 5 nm or greater), wherein seamless/voidless bottom-upgrowth of a layer is observed, when a film is deposited in a wide trenchhaving an aspect ratio of about 1 or more.

The flowability is often manifested as a concave surface of a film at abottom of a wide trench before filling the trench, and also manifestedas a substantially planar top surface of a film when being continuouslydeposited after completely filling the trench (planarization). Suchdeposition is referred to as “bottom-up deposition.”

When a trench is narrow and deep, even though a film is flowable, thefilm may not reach a bottom of the trench. In that case, the flowabilityis often manifested as a roughly or substantially conformal film alongsidewalls of the trench with substantially no film at a bottom of thetrench and typically with a top opening of the trench closed off by afilm. Since the film is flowable, the sidewall film flows and extendsdownward along the sidewalls, thereby forming a thin film, wherein aratio of averaged thickness of a substantially conformal part of thefilm (except a top part closing the top opening of the trench, which issubsequently removed by ashing) to depth of the film in the trench(length extended toward the bottom along the sidewall) may be in a rangeof 0.1% to 10% (typically 0.5% to 5%). Such deposition is referred to as“bottomless deposition”.

In this disclosure, a recess between adjacent protruding structures andany other recess pattern is referred to as a “trench”. That is, a trenchis any recess pattern including a hole/via. For bottom-up deposition, insome embodiments, the trench has a width of about 20 nm to about 100 nm(typically about 30 nm to about 50 nm) (wherein when the trench has alength substantially the same as the width, it is referred to as ahole/via), a depth of about 30 nm to about 100 nm (typically about 40 nmto about 60 nm), and an aspect ratio of about 2 to about 10 (typicallyabout 2 to about 5). Proper dimensions of the trench may vary dependingon the process conditions, flowability of the film, film compositions,intended applications, etc. By tuning the flowability of the film, forexample, bottom-up deposition can be realized in trenches having sizesdifferent from those described above.

In this disclosure, the term “substantially no deposition,”“substantially no film,” or the like refers to a quantity functionallyequivalent to zero, an immaterial or negligible quantity, a quantitywhich does not materially interfere with subsequent processes (e.g.,ashing), a quantity lower than a detectable or observable quantity, orthe like.

In this disclosure, any defined meanings do not necessarily excludeordinary and customary meanings in some embodiments. Also, in thisdisclosure, “the invention” or “the present invention” refers to atleast one of the embodiments or aspects explicitly, necessarily, orinherently disclosed herein.

Embodiments will be explained with respect to preferred embodiments.However, the present invention is not intended to be limited to thepreferred embodiments.

Some embodiments provide a method of top-selective deposition using aflowable carbon-based film on a substrate having a recess defined by atop surface, sidewall, and a bottom, comprising steps of: (i) depositinga flowable carbon-based film in the recess of the substrate in areaction space until a thickness of the flowable carbon-based film inthe recess reaches a predetermined thickness, and then stopping thedeposition step; and (ii) exposing the carbon-based film to a nitrogenplasma in an atmosphere substantially devoid of hydrogen and oxygen soas to redeposit a carbon-based film selectively on the top surface. Thecarbon-based film may typically be an amorphous carbon polymer filmwhich is a flowable film, but the carbon-based film can be any othersuitable carbon-based film which can be derived from a precursor andplasma-polymerized, and can be deposited in a flowable manner. Thecarbon-based film may contain Si (e.g., polycarbosilane polymer) or maybe free of Si (e.g., hydrocarbon polymer derived from cyclopentene).

When an amorphous carbon polymer film is formed by using aplasma-assisted method, the resultant amorphous carbon polymer film isconstituted by hydrogenated amorphous carbon polymer. In thisdisclosure, a hydrogenated amorphous carbon polymer may simply refer toan amorphous carbon polymer, which may also be referred to as “aC:H” orsimply “aC” as an abbreviation. Further, in this disclosure, SiC, SiCO,SiCN, SiCON, or the like is an abbreviation indicating a film type(indicated simply by primary constituent elements) in anon-stoichiometric manner unless described otherwise.

In some embodiments, steps (i) and (ii) are repeated multiple times(e.g., 1 to 100 times, typically 2 to 20 times) until a thickness of thecarbon-based film on the top surface reaches a desired final thickness(e.g., 1 to 100 nm, typically 2 to 20 nm) which may vary depending onits intended use and applications. When the carbon-based film reachesthe final thickness, and steps (i) and (ii) are stopped, the flowablecarbon-based film at the bottom of the recess can, if necessary, becompletely removed although its thickness has been reduced by step (ii);however, preferably, the final thickness of the carbon-based film on thetop surface is greater than the thickness of the flowable carbon-basedfilm at the bottom, so that when plasma aching (anisotropic) isconducted to further or completely remove the bottom carbon-based film,some thickness of the top carbon-based film can remain.

In some embodiments, the predetermined thickness in step (i) is morethan a monolayer thickness but 15 nm or less (preferably 7.5 nm or less,more preferably 5 nm or less), and steps (i) and (ii) are repeatedmultiple times.

Deposition of flowable film is known in the art; however, conventionaldeposition of flowable film uses chemical vapor deposition (CVD) withconstant application of RF power, since pulse plasma-assisted depositionsuch as PEALD is well known for depositing a conformal film which is afilm having characteristics entirely opposite to those of flowable film.In some embodiments, flowable film is a silicon-free carbon-containingfilm constituted by an amorphous carbon polymer, and although anysuitable one or more of hydrocarbon precursors can be candidates, insome embodiments, the precursor includes an unsaturated or cyclichydrocarbon having a vapor pressure of 1,000 Pa or higher at 25° C. Insome embodiments, the precursor is at least one selected from the groupconsisting of C2-C8 alkynes (C_(n)H_(2n−2)), C2-C8 alkenes(C_(n)H_(2n)), C2-C8 diene (C_(n)H_(n+2)), C3-C8 cycloalkenes, C3-C8annulenes (C_(n)H_(n)), C3-C8 cycloalkanes, and substituted hydrocarbonsof the foregoing. In some embodiments, the precursor is ethylene,acetylene, propene, butadiene, pentene, cyclopentene, benzene, styrene,toluene, cyclohexene, and/or cyclohexane.

In some embodiments, as the gap-fill technology for deposition offlowable film, the method disclosed in U.S. patent application Ser. No.16/026,711 and Ser. No. 16/427,288 can be used, which provides completegap-filling by plasma-assisted deposition using a hydrocarbon precursorsubstantially without formation of voids under conditions where anitrogen, oxygen, or hydrogen plasma is not required, the disclosure ofwhich is herein incorporated by reference in its entirety. Thedeposition process disclosed in the above references uses ALD-likerecipes (e.g., feed/purge/plasma strike/purge) wherein the purge afterfeed is voluntarily severely shortened to leave high partial pressure ofprecursor during the plasma strike. This is clearly distinguished fromALD chemistry or mechanism. The above processes can be based on pulseplasma CVD which also imparts good filling capabilities to resultantfilms although the ALD-like recipes may be more beneficial as discussedlater. In some embodiments, step (i) is conducted by cyclic nitrogenplasma deposition such as ALD-like deposition or pulse plasma CVD usinga nitrogen plasma.

In some embodiments, the atmosphere in step (ii) is in the reactionspace used in step (i), i.e., step (i) and step (ii) are conductedcontinuously in the same reaction space. Alternatively, in someembodiments, the atmosphere in step (ii) is in another reaction spacedifferent from the reaction space used in step (i).

In some embodiments, step (ii) comprises: feeding N₂ to the atmospherewithout feeding hydrogen and oxygen; and applying RF power to theatmosphere in a manner generating the nitrogen plasma. Applying RF powerto the atmosphere may be accomplished using a conductively coupledplasma (CCP) reactor or inductively coupled plasma (ICP) reactor, and insome embodiments, the nitrogen plasma may be generated as a remoteplasma using a remote plasma unit. In some embodiments, RF power is in arange of 0.14 W/cm² to 1.41 W/cm² per unit area of the substrate(preferably 0.3 to 0.9 W/cm²), and a duration of step (ii) is in a rangeof 10 seconds to 300 seconds (preferably 30 to 120 seconds).

In some embodiments, the method further comprises, after step (ii),removing a flowable carbon-based film at the bottom by O₂, H₂, O₂/Ar, orN₂/H₂ plasma ashing so that the target topology can be completelyachieved wherein a carbon-based film is deposited predominantly orsubstantially solely on the top surface of the substrate, among the topsurface, the sidewalls, and the bottom of the recess. In someembodiments, the plasma ashing is conducted using a direct or remoteoxygen or hydrogen plasma. In some embodiments, the direct or remoteoxygen or hydrogen plasma is a direct or remote plasma of gas(es)selected from the group consisting of solely H₂, a mixture of Ar and H₂(an Ar/H₂ flow ratio of 0.005 to 0.995, typically 0.05 to 0.75), amixture of He and H₂ (a He/H₂ flow ratio of 0.005 to 0.995, typically0.05 to 0.75), a mixture of N₂ and H₂ (an N₂/H₂ flow ratio of 0.005 to0.995, typically 0.05 to 0.75), solely O₂, a mixture of O₂ and Ar (anO₂/Ar flow ratio of 0.005 to 0.995, typically 0.05 to 0.75), a mixtureof O₂ and He (an O₂/He flow ratio of 0.005 to 0.995, typically 0.05 to0.75), a mixture of O₂ and N₂ (an O₂/N₂ flow ratio of 0.005 to 0.995,typically 0.05 to 0.75). In some embodiments, the top surface of thesubstrate on which the carbon-based film is redeposited is constitutedby silicon.

In some embodiments, the substrate has multiple recesses having aspectratios of 2 to 30 (typically 3 to 20), wherein the recesses are filledwith the film in a bottom-up manner in step (i) wherein there arevariations in surface topology due to the loading effect. However, insome embodiments, the height of the redeposited carbon-based film on thetop surfaces is about the same regardless of the width of the trenches(no loading effect). This may be due to the volumetric nature of thegrowth, i.e., the amount of material deposited in each trench before N₂treatment is about the same regardless of the width of the trenches(provided that the difference in the width is not extensive).

Embodiments will be explained with respect to the drawings. However, thepresent invention is not intended to be limited to the drawings.

FIG. 2 is a chart illustrating schematic cross sectional views oftrenches showing processes of top-selected deposition ((a)→(b)→(c)),based on the phenomena, according to embodiments of the presentinvention. First, in (a) of FIG. 2, bottom-up deposition is conducted ona substrate with trenches, wherein a substrate 21 has a trench 20 havinga width which is sufficiently wide to allow a flowable film to flow intothe trench, and having a depth which is sufficiently small to allow theflowable film to reach a bottom of the trench 20. As a result, theflowable film is deposited predominantly at the bottom of the trenches20 as a bottom flowable film 23 and partly on the top surface of thetrenches 20 as a top flowable film 22. Suitable sizes of trenches, byway of example, are described in this disclosure and can be selectedaccording to the flowability of the film, for example. It should benoted that FIG. 2 is overly simplified and is not scaled.

Next, in the redeposition process in (b), the bottom flowable film 23 isexposed to a nitrogen plasma, which generates gaseous species in thetrenches 20. The gaseous species are trapped in the trenches 20 andoccupies the trenches 20, reaching the top surface of the trenches 20(see FIG. 3 for more detailed explanation). In (c), the gaseous speciesdeposit (or redeposit) on the top surface of the trenches 20 andaccumulate thereon as a top film 24. This is accomplished in a mannersimilar to molecular beam epitaxy growth. It should be noted that theabove theory is a non-limiting theory of redeposition and does notnecessarily impose any limitation on this redeposition process.

FIG. 3 is a chart illustrating schematic cross sectional views oftrenches further showing a prospective mechanism of top-selecteddeposition ((a)→(b)→(c)→→(d)), based on a prospective mechanism,according to embodiments of the present invention. Step (a) in thisfigure is the same as step (a) of FIG. 2.

In (b), when the bottom flowable film 23 is exposed to the nitrogenplasma (anisotropic), etching of the bottom flowable film 23 (as well asthe top film 22) and formation of gaseous CxNyHz species (each of x, y,and z is an integer other than zero, formulating a stoichiometricchemical form) occur instantaneously, forming high density gaseousCxNyHz species 25 in the trenches 20 above an etched bottom flowablefilm 23′ while forming low density gaseous CxNyHz species 25′ above thetop surface. The above phenomena occur since the untreated flowablematerial constituting the flowable film is relatively fragile/lowquality.

In (c), the nitrogen plasma causes ion beam-like deposition since thenitrogen plasma is very directional (causing ion-assisted effect) in acertain pressure regime, e.g., in a range of 100 to 1000 Pa, preferably200 to 800 Pa, more preferably 300 to 700 Pa. The ion beam-likedeposition takes place instantaneously so that a top film 24′ isredeposited on the top surface, leaving a bottom flowable film 23″. Thetop-selected redeposition occurs probably because (a) there is verylittle or no deposition layer left on the top surface, and thus, sincethe sticking coefficient of the CxNyHz species is higher on the patternmaterial (silicon in this case) than is on the original flowable film,redeposition takes place predominantly on the top surface, and (b) inthe trenches 20, the density of the gaseous species is high, and thus,not enough ions can pass through the cloud of the gaseous species in thetrenches to the extent participating in the ion beam-like deposition atthe bottom. It should be noted that the above theory is a non-limitingtheory of redeposition and does not necessarily impose any limitation onthis redeposition process.

By repeating steps (a) to (c), the final structure shown in (d) isobtained, wherein a final top film 24 (“redeposited film”) isredeposited on the top surface, whereas substantially no film or littlefilm is left at the bottom of the trenches. The redeposited film 24 hasa composition and properties different from those of the top flowablefilm 22 or bottom flowable film 23 prior to the nitrogen plasmatreatment, wherein, in some embodiments, the redeposited film 24 has ahigher density (or higher RI), lower contact angle, higher compressivestress, lower thermal shrinkage, lower content of carbon, highernitrogen content, etc. as compared with those of the flowable film 22 or23. Thus, in some embodiments, the redeposited film is constituted by anitrocarbon-based film, as compared with the flowable film constitutedby a hydrocarbon-based film.

FIG. 10 is a chart illustrating the sequence of processes oftop-selected film formation according to an embodiment of the presentinvention, wherein the width of each column does not necessarilyrepresent the actual time length, and a raised level of the line in eachrow represents an ON-state whereas a bottom level of the line in eachrow represents an OFF-state.

This process sequence comprises a deposition process, “a×(aC depo)”(“Feed”→“Purge1”→“RF” (plasma polymerization)→“Purge2”; conducting atimes, i.e., repeating (a−1) times), a redeposition process, “N2Treatment” (“N2-In” (stabilization)→“N2 Treat” (redeposition)→“Purge3”),and an optional plasma ashing process, “O2/Ar or N2/H2 descum”(“N2/H2-In”→“Trim/Descum” (plasma ashing)→“Purge4”). The thickness offilm redeposited on the top surface at one time exposure to the nitrogenplasma is limited because the amount of gaseous species generated fromflowable film at one time exposure to the nitrogen plasma is limited dueto the limited depth (e.g., no more than 15 nm, 7.5 nm, or 5 nm) of theflowable film reached by the nitrogen plasma containing ions through thegaseous species cloud in the trenches as illustrated in FIG. 3 and/ordue to the limited depth of the flowable film generating the gaseousspecies due to the redeposition nature. The flowable film need notmaintain its flowability of the film (although in some embodiments, theflowability may be maintained) when being exposed to the nitrogen plasmasince the flowability is relatively quickly lost when being continuouslyexposed to the plasma for deposition and/or redeposition. The capabilityof redeposition may reside in the nature of flowable film, e.g., thefilm is an oligomeric product which is a soft/low density material ascompared to typical carbon-based film, and the nature makes itsusceptible to reaction with the nitrogen plasma and allows theredeposition process. In some embodiments, the thickness of theredeposited film at one time exposure to the nitrogen plasma is in arange of 2 to 20 nm, typically 5 to 15 nm, although the range varieswidely depending on the area of the top surface between the adjacenttrenches, the size of reservoir, i.e., the opening size and the depth offlowable film in the trench, the sticking degree of the gaseous species,and other conditions/parameters. Accordingly, steps (a) to (c)illustrated in FIG. 3 may be repeated in order to obtain the final filmhaving a desired thickness as shown in (d) of FIG. 3. In FIG. 10, whenthe deposition process, the nitrogen plasma treatment process, and theoptional plasma ashing process constitute one cycle of redeposition(overall cycle), the cycle may be conducted b times (i.e., repeated(b−1) times wherein b is an integer of 1 to 100, typically 2 to 15). Theashing process need not be conducted every time the overall cycle isrepeated and can be conducted intermittently as needed in relation tothe desired topology of the final film.

In some embodiments, the plasma polymerization process comprisesdepositing an amorphous carbon polymer film on a substrate havingtrenches by PEALD-like deposition using a Si- and metal-free,C-containing precursor and a plasma-generating gas which generates aplasma by applying RF power (RF) between two electrodes between whichthe substrate is placed in parallel to the two electrodes, wherein RFpower is applied in each sublayer deposition cycle of PEALD-likedeposition, wherein the plasma-generating gas and the carrier gas flowcontinuously and function also as a purging gas during “Purge1” andduring “Purge2”. The above processes are PEALD-like processes, one cycleof which for forming a sublayer (typically thicker than a monolayer) isconducted a times (e.g., a is an integer of 1 to 30, typically 2 to 15)until a thickness of the film reaches more than monolayer thickness but15 nm or less (e.g., 1 nm to 7.5 nm).

In some embodiments, the feed time is in a range of 0.3 to 10 seconds(typically 0.6 to 2 seconds), the purge time after the feed is in arange of 0 to 0.1 seconds (typically 0 to 0.5 seconds), the RF time isin a range of 0.5 to 4 seconds (typically 0.8 to 2 seconds), the purgetime after the RF is in a range of 0 to 0.5 seconds (typically 0 to 0.1seconds), the carrier gas flow is in a range of 0 to 0.8 slm (typically0.1 to 0.3 slm), the plasma-generating gas flow is in a range of 0 to0.5 slm (typically 0.1 to 0.3 slm), and the RF power is in a range of 50to 400 W (typically 75 to 200 W) for a 300-mm wafer (for different sizewafers, the above wattage is applied as W per unit area (cm²) of eachwafer).

The flowability of film is temporarily obtained when a volatilehydrocarbon precursor, for example, is polymerized by a plasma anddeposited on a surface of a substrate, wherein gaseous monomer(precursor) is activated or fragmented by energy provided by plasma gasdischarge so as to initiate polymerization, and when the resultantpolymer material is deposited on the surface of the substrate, thematerial shows temporarily flowable behavior. When the deposition stepis complete, the flowable film is no longer flowable but is solidified,and thus, a separate solidification process is not required.

Next, the redeposition process begins, which comprises stopping feedingdilution He and starting feeding nitrogen gas (“N2-In”), whilecontinuously feeding carrier He (in some embodiments, Ar and/or N₂,alternatively or additionally, can be used as a carrier gas) whichshould be limited to, e.g., less than 50% of the gas mixture in thereaction space, preferably less than 30%, more preferably less than 20%,typically less than 15%, for effective redeposition. In someembodiments, the nitrogen gas flow is in a range of 0.5 to 20 slm(typically 1 to 3 slm). RF power is then applied to the reaction spacefor generating a nitrogen plasma and exposing the flowable amorphouscarbon polymer film thereto (“N2 Treat”), wherein the RF power is in arange of 100 to 1,000 W (preferably 200 to 800 W, more preferably 300 to700 W) for a 300-mm wafer (for different size wafers, the above wattageis applied as W per unit area (cm²) of each wafer) under a pressure of100 to 1,000 Pa (preferably 600 Pa or less, more preferably 400 Pa orless) for a duration of 5 to 300 seconds (preferably 20 to 120 seconds,more preferably 30 to 90 seconds). Thereafter, purging begins(“Purge3”), wherein the purge time after the nitrogen plasma treatmentis in a range of 0 to 60 seconds (preferably 10 to 30 seconds). Duringthe redeposition process, since H₂ addition to N₂ plasma only leads toashing (not contributing to redeposition and top selectivity), the gasmixture during the redeposition treatment should be substantially devoidof H₂ and O₂, e.g., preferably less than 5%, more preferably less than1% or substantially 0%.

Next, depending on the target topology of the final carbon-based film,the optional plasma ashing process begins, which comprises feeding anashing gas (H₂ or O₂, or a mixture of the foregoing and N₂, Ar, and/orHe) to the reaction space (“N2/H2-In”) which is excited by RF power togenerate a plasma and ash the amorphous carbon polymer film(“Trim/Descum”), followed by purging (“Purge4”), wherein feeding thedilution He begins while the carrier gas is fed continuously to thereaction space. In some embodiments, the RF power for the plasma ashingis in a range of 50 to 500 W (typically 50 to 200 W) under a pressure of100 Pa to 1000 Pa (typically 200 to 600 Pa) for a duration of 5 to 200seconds (typically 10 to 100 seconds), the stabilization time is in arange of 5 to 60 seconds (typically 10 to 30 seconds), the purge timeafter the RF is in a range of 5 to 60 seconds (typically 10 to 30seconds), and the ashing gas flow is in a range of 0.1 to 10 slm(typically 0.5 to 2 slm).

In some embodiments, throughout the entirety of the processes, thecarrier gas is fed continuously to the reaction space. Also, thetemperature of the processes is adjusted so as to realize flowability ofthe amorphous carbon polymer film and allow for redeposition of thenitrogen-doped hydrocarbon polymer film, e.g., in a range of −50° C. to175° C. (preferably 35° C. to 150° C.).

The continuous flow of the carrier gas can be accomplished using aflow-pass system (FPS) wherein a carrier gas line is provided with adetour line having a precursor reservoir (bottle), and the main line andthe detour line are switched, wherein when only a carrier gas isintended to be fed to a reaction chamber, the detour line is closed,whereas when both the carrier gas and a precursor gas are intended to befed to the reaction chamber, the main line is closed and the carrier gasflows through the detour line and flows out from the bottle togetherwith the precursor gas. In this way, the carrier gas can continuouslyflow into the reaction chamber, and can carry the precursor gas inpulses by switching between the main line and the detour line. FIG. 1Billustrates a precursor supply system using a flow-pass system (FPS)according to an embodiment of the present invention (black valvesindicate that the valves are closed). As shown in (a) in FIG. 1B, whenfeeding a precursor to a reaction chamber (not shown), first, a carriergas such as Ar (or He) flows through a gas line with valves b and c, andthen enters a bottle (reservoir) 26. The carrier gas flows out from thebottle 26 while carrying a precursor gas in an amount corresponding to avapor pressure inside the bottle 26, and flows through a gas line withvalves f and e, and is then fed to the reaction chamber together withthe precursor. In the above, valves a and d are closed. When feedingonly the carrier gas (noble gas) to the reaction chamber, as shown in(b) in FIG. 1B, the carrier gas flows through the gas line with thevalve a while bypassing the bottle 26. In the above, valves b, c, d, e,and f are closed.

The process cycle can be performed using any suitable apparatusincluding an apparatus illustrated in FIG. 1A, for example. FIG. 1A is aschematic view of a PEALD apparatus, desirably in conjunction withcontrols programmed to conduct the sequences described below, usable insome embodiments of the present invention. In this figure, by providinga pair of electrically conductive flat-plate electrodes 4, 2 in paralleland facing each other in the interior 11 (reaction zone) of a reactionchamber 3, applying HRF power (13.56 MHz-2000 MHz) 25 to one side, andelectrically grounding the other side 12, a plasma is excited betweenthe electrodes. A temperature regulator is provided in a lower stage 2(the lower electrode), and a temperature of a substrate 1 placed thereonis kept constant at a given temperature. The upper electrode 4 serves asa shower plate as well, and reactant gas and/or dilution gas, if any,and precursor gas are introduced into the reaction chamber 3 through agas line 27 and a gas line 28, respectively, and through the showerplate 4. Additionally, in the reaction chamber 3, a circular duct 13with an exhaust line 7 is provided, through which gas in the interior 11of the reaction chamber 3 is exhausted. Additionally, a transfer chamber5 disposed below the reaction chamber 3 is provided with a seal gas line29 to introduce seal gas into the interior 11 of the reaction chamber 3via the interior 16 (transfer zone) of the transfer chamber 5 wherein aseparation plate 14 for separating the reaction zone and the transferzone is provided (a gate valve through which a wafer is transferred intoor from the transfer chamber 5 is omitted from this figure). Thetransfer chamber is also provided with an exhaust line 6. In someembodiments, the deposition of multi-element film and surface treatmentare performed in the same reaction space, so that all the steps cancontinuously be conducted without exposing the substrate to air or otheroxygen-containing atmosphere.

In some embodiments, in the apparatus depicted in FIG. 1A, the system ofswitching flow of an inactive gas and flow of a precursor gasillustrated in FIG. 1B (described earlier) can be used to introduce theprecursor gas in pulses without substantially fluctuating pressure ofthe reaction chamber.

A skilled artisan will appreciate that the apparatus includes one ormore controller(s) (not shown) programmed or otherwise configured tocause the deposition and reactor cleaning processes described elsewhereherein to be conducted. The controller(s) are communicated with thevarious power sources, heating systems, pumps, robotics, and gas flowcontrollers, or valves of the reactor, as will be appreciated by theskilled artisan.

In some embodiments, a dual chamber reactor (two sections orcompartments for processing wafers disposed close to each other) can beused, wherein a reactant gas and a noble gas can be supplied through ashared line whereas a precursor gas is supplied through unshared lines.

The film having filling capability can be applied to varioussemiconductor devices including, but not limited to, cell isolation in3D cross point memory devices, self-aligned Via, dummy gate (replacementof current poly Si), reverse tone patterning, PC RAM isolation, cut hardmask, and DRAM storage node contact (SNC) isolation.

EXAMPLES

In the following examples where conditions and/or structures are notspecified, the skilled artisan in the art can readily provide suchconditions and/or structures, in view of the present disclosure, as amatter of routine experimentation. A skilled artisan will appreciatethat the apparatus used in the examples included one or morecontroller(s) (not shown) programmed or otherwise configured to causethe deposition and reactor cleaning processes described elsewhere hereinto be conducted. The controller(s) were communicated with the variouspower sources, heating systems, pumps, robotics and gas flow controllersor valves of the reactor, as will be appreciated by the skilled artisan.

Reference Example 1 (FIG. 4)

A flowable amorphous carbon polymer film (a-C blanket layer) wasdeposited using cyclopentene at a thickness of 100-150 nm on a Sisubstrate (having a diameter of 300 mm and a thickness of 0.7 mm) byPEALD-like process which is defined in U.S. patent application Ser. No.16/026,711 and Ser. No. 16/427,288, following the deposition processillustrated in FIG. 10 under the conditions shown in Table 1 below usingthe apparatus illustrated in FIG. 1A and a gas supply system (FPS)illustrated in FIG. 1B. Post-deposition plasma treatment was conductedon the flowable amorphous carbon polymer film under the conditions shownin Table 1 below, which was conducted in the same reaction chamber as inthe deposition process, in order to evaluate film shrinkage effect byeach post-deposition treatment.

TABLE 1 (numbers are approximate) Depo SUS temp (° C.). 70 SHD temp (°C.) 75 Wall temp (° C.) 75 BLT temp (° C.) RT Pressure (Pa) 1100 Gap(mm) 14 Feed time (s) 0.4 Purge (s) 0.1 RF time (s) 1.5 Purge (s) 0.1 RFpower (W) 230 The number of depo 242 . . . cycles (a in FIG. 10)Precursor Cyclopentene Carrier He Carrier flow (slm) 0.1 Dry He (slm)0.2 Seal He (slm) 0.1 Plasma Temperature (° C.) 200 treatment Pressure(Pa) 400 Treatment gas Ar; H₂; O₂/Ar (0.5/0.5); N₂; N₂/H₂ (0.5/0.5)Treatment gas flow (slm) . . . 1 Stabilization (s) 15 RF time (s) 360 RFpower (W) 200 Purge (s) Not applicable The number of overall cycles Notapplicable (b in FIG. 10)

Further, all the data reported in FIG. 10 on aching were done on a layerwhich underwent no nitrogen plasma treatment cycles.

FIG. 4 is a graph showing the results: shrinkage of the films exposed tothe plasma of different gases. As shown in FIG. 4, the effect ofpost-deposition plasma treatment on the blanket layer of flowable aCvaries depending on the gas type as follows:

Ar: a small thickness decrease (this effect saturates if the treatmentis prolonged)→Densification;

H₂: a huge thickness loss (this effect does not saturate but ashes allthe film if the treatment is prolonged)→“Normal” ashing/dry etch effect;

N₂/H₂: a huge thickness loss (this effect does not saturate but ashesall the film if the treatment is prolonged, see also FIG. 5)→“Normal”ashing/dry etch effect;

O₂/Ar: a huge thickness loss (this effect does not saturate but ashesall the film if the treatment is prolonged, see also FIG. 5)→“Normal”ashing/dry etch effect; and

N₂: a thickness increase→Opposite to “normal” ashing/dry etch effect.

Surprisingly, the nitrogen plasma treatment conducted on the flowablea-C film caused redeposition (sticking) of the gaseous species generatedby the plasma.

Reference Example 2 (FIG. 5)

A flowable amorphous carbon polymer film (a-C film) was deposited on aSi substrate (having a diameter of 300 mm and a thickness of 0.7 mm)having trenches with an opening of approximately 25 to 100 nm, which hada depth of approximately 85 nm (an aspect ratio was approximately 3.4 to0.85), by PEALD-like process in a bottom-up manner in the same mannerunder the same conditions as those in Reference Example 1 except thatthe deposition continued until the trenches were fully filled and thetop surface of the a-C film became planar. Thereafter, thepost-deposition plasma treatment was conducted in the same manner underthe same conditions as those using O₂/Ar and N₂/H₂ in Reference Example1 except that the plasma treatment continued until all the film wasremoved.

FIG. 5 shows STEM photographs of cross-sectional views of the trenches,wherein raw (a) represents the trenches subjected to full-filldeposition of the flowable film, raw (b) represents the trenches shownin (a) after O₂/Ar ashing, and raw (c) represents the trenches shown in(a) after N₂/H₂ ashing, and column (1) represents the trenches at a highmagnification (the scale bar represents 60 nm), and column (2)represents the trenches at low magnification (the scale bar represents300 nm). It is confirmed that both O₂/Ar ashing and N₂/H₂ ashing lead tocomplete removal of the film.

Example 1 and Comparative Example 1 (FIG. 6)

In Example 1, a flowable amorphous carbon polymer film (a-C film) wasdeposited on a Si substrate (having a diameter of 300 mm and a thicknessof 0.7 mm) having trenches with an opening of approximately 70 to 100nm, which had a depth of approximately 85 nm (an aspect ratio wasapproximately 1.2 to 0.85), by PEALD-like process in a bottom-up mannerin the same manner under the same conditions as those in ReferenceExample 1 except that the deposition cycle was conducted 36 (3 times 12depo cycle+N₂ plasma treat) times. In Comparative Example 1, anamorphous carbon polymer film was deposited in the same manner as inExample 1 except that the deposition temperature (the temperature of thesusceptor and the walls) was 100° C. as compared with 75° C. inExample 1. Thereafter, the cyclic nitrogen plasma treatment wasconducted on each film in the same manner under the same conditions asthose using N2 as the post-treatment gas in Reference Example 1 exceptthat the nitrogen plasma treatment was conducted for 60 seconds.

FIG. 6 shows: (a) a STEM photograph of a cross-sectional view of thetrenches subjected to film deposition at 75° C., followed by exposure toN2 plasma in Example 1, and (b) a STEM photograph of a cross-sectionalview of the trenches subjected to film deposition at 100° C., followedby exposure to N2 plasma in Comparative Example 1. It can be seen fromFIG. 6 that the nitrogen plasma treatment was not the sole parameterresponsible for the top selectivity, i.e., although both films receivedthe same deposition cyclic treatment and the same nitrogen plasmatreatment, one (Example 1) was deposited at 75° C. and the other(Comparative Example 1) was deposited at 100° C., resulting insignificantly topological differences in the final films. Consideringthat flowability of deposited film is inversely proportional to thedeposition temperature and that the film deposited at 75° C. wasflowable whereas the film deposited at 100° C. was barely flowable, theabove topological differences are expected to reside in the reason thatonly flowable (weak, fragile, low-quality) layer when receiving N₂plasma can form the gaseous species that will lead to redeposition andtop selectivity. By adjusting not only the deposition temperature butalso other process parameters, film can be deposited while maintainingflowability, and when being exposed to nitrogen plasma, top-selectivetopology of the final film can be obtained. A skilled artisan in the artcan readily provide such conditions and/or structures, in view of thepresent disclosure, as a matter of routine experimentation.

Example 2 and Comparative Example 2 (FIG. 7)

In Example 2, a flowable amorphous carbon polymer film (a-C film) wasdeposited on a Si substrate (having a diameter of 300 mm and a thicknessof 0.7 mm) having trenches with an opening of approximately 70 to 100nm, which had a depth of approximately 85 nm (an aspect ratio wasapproximately 1.2 to 0.85), by PEALD-like process in a bottom-up mannerin the same manner under the same conditions as those in Example 1.Thereafter, the post-deposition nitrogen plasma treatment was conductedon the film in the same manner under the same conditions as inExample 1. In Comparative Example 2, the same processes under the sameconditions as in Example 2 were conducted except that the nitrogenplasma treatment was conducted for 10 seconds as compared with 60seconds in Example 2.

FIG. 7 shows: (a) a STEM photograph of a cross-sectional view of thetrenches subjected to flowable film deposition, followed by exposure toN2 plasma for 10 seconds in Comparative Example 2, and (b) a STEMphotograph of a cross-sectional view of the trenches subjected toflowable film deposition, followed by exposure to N2 plasma for 60seconds in Example 2. It can be seen from FIG. 7 that longer N₂ plasmatreatment is beneficial for the top-topology selectivity. By adjustingthe duration of the nitrogen plasma treatment, film can be deposited ina top-selective manner. A skilled artisan in the art can readily providesuch conditions and/or structures, in view of the present disclosure, asa matter of routine experimentation.

Example 3 (Table 2, FIG. 9)

In Example 3, an amorphous carbon polymer film was formed in the samemanner under the same conditions as in Example 1, and then, the nitrogenplasma treatment was conducted on the film in the same manner under thesame conditions as in Example 1 to obtain a redeposited amorphous carbonpolymer film on the top surface of the trenches. The properties of theresultant amorphous carbon polymer films were evaluated. The results areshown in Table 2 below and FIG. 9.

TABLE 2 (numbers are approximate) STD-film Redeposited film (No N2 (N2plasma plasma) treated) Deposition Rate [nm/min] 12 2.5 RI 1.54 1.61Water Contact Angle [°] (25° C.) 66.1 46.1 Stress [MPa] ~0 −80 RBS [%] C51.0 40.0 H 46.0 40.2 O 3.0 3.5 N ND 16.3 Thermal  50° C./30 min 0 —shrinkage [%] 125° C./30 min 10-20 — 200° C./30 min 17.6 7.6 300°C./30min 35.4 23.9

As shown in Table 2, the thermal shrinkage of the amorphous carbonpolymer film with the nitrogen plasma treatment (“Redeposited film”) wasremarkably lower than that of the amorphous carbon polymer film withoutplasma treatment (“STD-film”, standard film), indicating that thethermal stability of the redeposited film was improved. Further, thecomposition analysis shows that the redeposited film was anitrogen-doped hydrocarbon film, whereas the standard film was ahydrocarbon film. Furthermore, the redeposited film had higher RI(higher density), lower contact angle, and higher compressive stressthan those of the standard film. In addition, FIG. 10 shows FourierTransform Infrared (FTIR) spectrums of the amorphous carbon polymer filmas deposited (“STD”), and the redeposited amorphous carbon polymer filmwith N₂ plasma treatment (“N2-CK”). As shown in FIG. 9, the redepositedfilm developed —NH bonds and —R—N—C bonds, and considering the resultsshown in Table 2, the redeposited film was likely to have promotedfurther polymerization of the film matrix and doped with nitrogen,thereby reducing thermally unstable hydrogen-related fractions such asmethyl and/or methylene fractions from the amorphous carbon polymerfilm. It should be noted that oxygen atoms were detected in each film,and it may be because the films were exposed to the air after thesubstrates were taken out from the reaction chamber.

In some embodiments, the standard film is a hydrogenated amorphouscarbon polymer having a composition constituted by more than 50% ofcarbon atoms and more than 35% but less than 50% of hydrogen atoms (asmeasured using, e.g., Rutherford backscattering Spectrometry (RBS)),whereas the redeposited film is a nitrogen-doped hydrogenated amorphouscarbon polymer having a composition constituted by more than 35% butless than 50% of carbon atoms and more than 35% but less than 50% ofhydrogen atoms, and more than 10% but less than 20% of nitrogen atoms.

Example 4 (FIG. 8)

In Example 4, a flowable amorphous carbon polymer film (a-C film) wasdeposited on a Si substrate (having a diameter of 300 mm and a thicknessof 0.7 mm) having trenches with an opening of approximately 70 to 100nm, which had a depth of approximately 85 nm (an aspect ratio wasapproximately 1.2 to 0.85), by PEALD-like process in a bottom-up mannerin the same manner under the same conditions as those in Example 1.Thereafter, the post-deposition nitrogen plasma treatment was conductedon the film in the same manner under the same conditions as inExample 1. However, in Example 4, the overall cycle was conducted 25times (12 depo cycle+N2 plasma treat).

FIG. 8 shows a STEM photograph of a cross-sectional view of the trenchessubjected to the top-selected deposition in Example 4. As shown in FIG.8, remarkable top-selective topology of the film was achieved, whereinthe thickness of the redeposited film on the top surface was about 145nm, whereas the thickness of the film at the bottom of the trenches wasabout 1 to 3 nm. The bottom film can be substantially or completelyremoved by plasma aching (although the deposited film also is ached to anearly same degree as in the bottom film, since the thickness differencebetween the top film and the bottom film is so great that a reduction ofthickness of the top film is negligible).

It will be understood by those of skill in the art that numerous andvarious modifications can be made without departing from the spirit ofthe present invention. Therefore, it should be clearly understood thatthe forms of the present invention are illustrative only and are notintended to limit the scope of the present invention.

We/I claim:
 1. A method of top-selective deposition using a flowablecarbon-based film on a substrate having a recess defined by a topsurface, sidewall, and a bottom, comprising steps of: (i) depositing aflowable carbon-based film in the recess of the substrate in a reactionspace until a thickness of the flowable carbon-based film in the recessreaches a predetermined thickness, and then stopping the depositionstep; and (ii) exposing the carbon-based film to a nitrogen plasma in anatmosphere substantially devoid of hydrogen and oxygen so as toredeposit a carbon-based film selectively on the top surface.
 2. Themethod according to claim 1, wherein steps (i) and (ii) are repeatedmultiple times until a thickness of the carbon-based film on the topsurface reaches a desired final thickness.
 3. The method according toclaim 1, wherein the predetermined thickness in step (i) is more than amonolayer thickness but 15 nm or less.
 4. The method according to claim1, wherein the atmosphere in step (ii) is in the reaction space used instep (i).
 5. The method according to claim 1, wherein the atmosphere instep (ii) is in another reaction space different from the reaction spaceused in step (i).
 6. The method according to claim 1, wherein step (ii)comprises: feeding N₂ to the atmosphere without feeding hydrogen andoxygen; and applying RF power to the atmosphere in a manner generatingthe nitrogen plasma.
 7. The method according to claim 6, wherein RFpower is in a range of 0.14 W/cm² to 1.41 W/cm² per unit area of thesubstrate, and a duration of step (ii) is in a range of 10 seconds to300 seconds.
 8. The method according to claim 1, wherein step (i) isconducted by cyclic nitrogen plasma deposition.
 9. The method accordingto claim 1, wherein the top surface of the substrate on which thecarbon-based film is redeposited is constituted by silicon.
 10. Themethod according to claim 1, further comprising, after step (ii),removing a flowable carbon-based film at the bottom by O₂, H₂, O₂/Ar, orN₂/H₂ plasma aching.
 11. The method according to claim 1, wherein thecarbon-based film is an amorphous carbon film.
 12. The method accordingto claim 1, wherein the deposited flowable carbon-based film isconstituted by a hydrogenated amorphous carbon polymer, whereas theredeposited carbon-based film is constituted by a nitrogen-dopedhydrogenated amorphous carbon polymer.